JP2009230869A - Gas diffusion layer for fuel cell - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a gas diffusion layer for a fuel cell, which can excellently ensure conductivity even if formed from a non-conductive porous resin material. <P>SOLUTION: The gas diffusion layer 20 is constituted of: a main body 21 formed from the non-conductive porous resin material; a carbon thin film layer 22 formed on a facing surface facing an MEA 10 of the main body 21; and a plurality of carbon rods 23 joined integrally with the carbon thin film layer 22. As a result, electrons generated by electrode reaction of the MEA 10 can be extremely easily moved to the carbon thin film layer 22 formed from carbon excellent in conductivity, and also can be moved to the carbon rods 23 joined integrally with the carbon thin film layer 22 without any loss. Then, the electrons can be moved from the carbon rods 23 to a current-collecting plate 30. At this time, since a plurality of carbon rods 23 are provided, contact resistance between the carbon rods 23 and the current-collecting plate 30 can be reduced to a large extent. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a gas diffusion layer employed in a fuel cell, in particular, a polymer electrolyte fuel cell.

  Conventionally, for example, a fuel cell as shown in Patent Document 1 below is known. In this conventional fuel cell, an opening diameter is formed from a current collector that is formed of carbon or metal and has a gas introduction function and collects the generated electricity toward the catalyst layer that constitutes the electrode / electrolyte assembly. A laminate in which a porous layer formed of carbon or metal is laminated so as to decrease is used as a diffusion layer. As a result, the reaction gas can be efficiently supplied to the entire catalyst layer, and a fuel cell with high output and high energy efficiency can be obtained.

  By the way, as for the fuel cell, it goes without saying that the power generation is improved, and the development of an inexpensive and lightweight battery while ensuring sufficient durability has been actively studied. Here, in the conventional fuel cell, since the current collector has a gas introduction function, for example, when a metal current collector is employed, there is a concern about an increase in the weight of the fuel cell. Further, when the diffusion layer is formed using a metal porous layer, the durability of the fuel cell may be impaired by metal ions eluted from the catalyst layer. On the other hand, by making the current collector and the diffusion layer made of carbon, these concerns can be solved. However, for producing a porous material made of carbon, for example, a high temperature atmosphere is required, and thus the production cost is low. As a result, the fuel cell itself may be expensive.

For such a problem, for example, as shown in Patent Document 2 and Patent Document 3 below, it is effective to form a separator having a gas introduction function and a diffusion layer using a porous resin material. Thereby, durability is ensured and it is thought that a cheap and lightweight fuel cell is obtained.
JP 2000-58073 A JP 2007-128803 A Japanese Patent Laid-Open No. 11-204114

  By the way, it is generally said that the conductivity of a resin material is inferior to that of a metal material or a carbon material. In this case, for example, as shown in Patent Document 3 described above, by adding a conductor to the resin material, the conductivity of the resin material is somewhat improved, but it has sufficient conductivity. It ’s not good. Furthermore, when the diffusion layer and the separator are formed using a resin material, the electricity generated by the electrode reaction in the electrode / electrolyte assembly (electrode structure) is transferred from the catalyst layer (electrode catalyst layer) to the diffusion layer and separator. Therefore, there is a possibility that the contact resistance between the members is added and the generated electricity cannot be output efficiently. In addition, although the said patent document 2 has provided the electroconductive pin with respect to a separator and it is shown outputting the generated electricity efficiently to the exterior, in this case, an electroconductive pin is gas diffusion. It will contact both the material (carbon paper or carbon cloth) and the current collector. In particular, the contact between the thin gas diffusion material and the conductive pin is likely to reduce the contact area due to the surface state of the catalyst layer (electrode catalyst layer), and as a result, the contact resistance may be further increased. is there.

  The present invention has been made to solve the above-described problems, and its purpose is to provide a gas diffusion for fuel cells that can ensure good conductivity even when formed from a non-conductive porous resin material. To provide a layer.

  In order to achieve the above object, a feature of the present invention is that it is disposed between an electrode catalyst layer constituting an electrode structure of a fuel cell and a current collector that collects electricity generated by the electrode structure. In the gas diffusion layer for a fuel cell for diffusing and supplying a predetermined gas to the electrode catalyst layer, the fuel cell gas diffusion layer is formed of a non-conductive porous resin material, and diffuses the predetermined gas to be conductive. A flat main body, a thin film layer formed on an opposing surface of the main body facing the electrode catalyst layer and having a thickness smaller than a radius of an opening on the opposing surface; and the thin film layer, A conductive member that is formed of the same material and that electrically connects the current collector and the thin film layer that is in contact with the electrode catalyst layer through the main body; and the thin film layer and the conductive member Is integrally joined. In this case, the thin film layer and the conductive member may be formed of carbon, for example.

  According to these, the gas diffusion layer can be formed using an inexpensive and light non-conductive porous resin material. Thereby, there is no elution of metal ions, and the durability of the fuel cell can be sufficiently ensured. In addition, in order to ensure the conductivity of the gas diffusion layer formed from a non-conductive porous resin material, for example, carbon having excellent conductivity is formed on the opposing surface of the main body facing the electrode catalyst layer. The used thin film layer can be formed. Here, the contact state (contact area) between the electrode catalyst layer and the thin film layer can be satisfactorily ensured by forming a thin film layer having conductivity with respect to the opposing surface. Thereby, the generated electricity (more specifically, electrons generated by the electrode reaction) can be transmitted from the electrode catalyst layer to the thin film layer or from the thin film layer to the electrode catalyst layer with reduced loss.

  Moreover, when forming a thin film layer, it forms so that the film thickness may become smaller than the radius of the opening in an opposing surface. Accordingly, the formed thin film layer can be prevented from closing the opening on the opposing surface, and a predetermined gas (fuel gas or oxidant gas) that conducts in the main body can be sufficiently supplied to the electrode catalyst layer. .

  In addition, since the conductive member formed of the same material (for example, carbon) can be integrally bonded to the formed thin film layer, the contact resistance between the thin film layer and the conductive member is substantially “0”. It can be. Therefore, the generated electricity (more specifically, electrons generated by the electrode reaction) can be transmitted without loss from the thin film layer to the conductive member or from the conductive member to the thin film layer. And since a conductive member can penetrate a main body and can electrically connect a thin film layer and a collector, it can output generated electricity efficiently via a collector.

  Moreover, the said thin film layer is good to be formed in the said opposing surface of the said main body in the state in which the said electrically-conductive member penetrated the said main body, for example. According to this, the thin film layer can be formed by being integrally bonded to the conductive member. Therefore, the conductivity of the gas diffusion layer can be ensured satisfactorily.

  In this case, the thin film layer may be formed by vapor deposition on the facing surface of the main body. According to this, the thin film layer and the conductive member can be reliably joined together, and a smooth thin film layer having a uniform layer thickness can be formed. Therefore, the contact state (contact area) between the electrode catalyst layer and the thin film layer can be secured better, and the conductivity of the gas diffusion layer can be secured better. In addition, since a uniform layer thickness can be ensured, it is possible to more reliably prevent the thin film layer from blocking the opening on the opposite surface.

  The conductive member may be provided in a plurality with respect to the main body. According to this, since the contact portion between the conductive member and the current collector, in other words, the contact area can be increased, the contact resistance between the conductive member and the current collector can be further reduced. Therefore, the generated electricity can be output more efficiently through the current collector.

  In this case, the conductive member is formed in a rod shape, for example, and is preferably press-fitted into a plurality of through holes formed in the main body. According to this, for example, since the conductive member formed in a bar shape can be press-fitted into the through hole formed in the main body, the displacement of the conductive member with respect to the main body can be regulated. Thereby, even when the fuel cell is formed, the contact state of the conductive member with respect to the thin film layer and the current collector (particularly, the contact state between the conductive member and the current collector) can be satisfactorily maintained. it can. Therefore, the generated electricity can be output efficiently over a long period of time.

  The main body may be formed of a porous resin material having an opening radius that increases from the current collector toward the electrode catalyst layer. According to this, the main body can absorb excess water generated particularly on the cathode electrode side to a position away from the electrode catalyst layer by an electrode reaction in the electrode structure. Further, since the radius of the opening on the opposing surface of the main body is increased, it is possible to effectively prevent the opening from being blocked even if a thin film layer is formed. Therefore, the main body can satisfactorily supply a predetermined gas to the electrode catalyst layer, and as a result, a decrease in power generation efficiency of the fuel cell can be suppressed.

  In this case, the main body is disposed on the electrode catalyst layer side and is formed on the current collector side with the first layer formed of the first porous resin material having a large opening radius. It is good to comprise including the 2nd layer formed from the 2nd porous resin material whose opening radius is smaller than the 1st porous material. According to this, the radius of the opening in the main body can be made different between the electrode catalyst layer side and the current collector side very easily and inexpensively. Therefore, also in this case, the main body can supply a predetermined gas to the electrode catalyst layer satisfactorily, and as a result, it is possible to suppress a decrease in power generation efficiency of the fuel cell.

  Another feature of the present invention is that the electrode catalyst layer is electrically divided within the layer, and the thin film layer and the current collector are electrically connected to the divided electrode catalyst layer. There is also to divide. According to this, it becomes possible to connect in series and in parallel in the fuel cell, or to change the voltage in the fuel cell. Therefore, for example, even when the installation space of the fuel cell is limited, the electricity required by one fuel cell can be supplied.

  Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. FIG. 1 schematically shows a main part of a single cell T of a polymer electrolyte fuel cell employing a gas diffusion layer according to the present invention. The unit cell T includes an MEA (Membrane-Electrode Assembly) 10 as an electrode structure, a fuel gas (for example, hydrogen gas) and an oxidant gas (for example, air) introduced from the outside of the fuel cell. The gas diffusion layer 20 that conducts and diffuses and supplies the MEA 10 to the MEA 10, the current collector 30 as a current collector for collecting electricity generated by the electrode reaction by the MEA 10, and a resin frame (gasket) (not shown) Has been.

The MEA 10 includes an electrolyte membrane 11 as shown in FIG. The electrolyte membrane 11 is formed of an ion exchange membrane (for example, Nafion (registered trademark) manufactured by DuPont) that selectively transmits hydrogen ions (H ⁺ ). Then, a catalyst layer 12 as an electrode catalyst layer on the surface of the electrolyte membrane 11 to which the fuel gas is supplied, that is, the anode electrode side is formed, and a catalyst layer as an electrode catalyst layer on the surface to which the oxidant gas is supplied, that is, the cathode electrode side. 13 is formed.

The catalyst layer 12 on the anode electrode side and the catalyst layer 13 on the cathode electrode side are formed mainly of carbon (hereinafter referred to as supported carbon) supporting a noble metal catalyst (for example, platinum). The catalyst layers 12 and 13 are formed in layers by, for example, hot pressing after applying supported carbon dispersed in a solvent on both surfaces of the electrolyte membrane 11. The catalyst layer 12 thus formed ionizes the supplied fuel gas, that is, hydrogen gas, into hydrogen ions (H ⁺ ) and electrons. In addition, the catalyst layer 13 includes supplied oxidant gas, that is, oxygen in the air, hydrogen ions (H ⁺ ) that have passed through the electrolyte membrane 11 from the anode electrode side, and electrons supplied from the catalyst layer 12 on the anode electrode side. To produce water.

  As shown in a partially enlarged view in FIG. 2, the residue diffusion layer 20 includes a main body 21, a carbon thin film layer 22 as a thin film layer, and a carbon rod 23 as a conductive member. The main body 21 is formed from a non-conductive porous resin material (for example, Fildus (registered trademark) manufactured by Mitsubishi Plastics, Inc.) and has a thickness of about 2 mm, for example. And as shown in FIG. 2, the main body 21 is made into the laminated structure which has the 1st layer 21a and the 2nd layer 21b. The first layer 21a disposed on the MEA 10 side is formed of a first porous resin material having a large opening radius (average radius) (for example, about 10 μm), and is disposed on the current collector plate 30 side. The layer 21b is formed of a second porous resin material whose opening radius is smaller (for example, about 1 μm) than the opening radius of the first porous resin. The main body 21 has a plurality of through holes 21c that open in the stacking direction of the first layer 21a and the second layer 21b.

  The carbon thin film layer 22 is formed, for example, by vapor-depositing carbon on the surface (facing surface) facing the MEA 10 of the first layer 21a constituting the main body 21 by a known sputtering method, and has a film thickness of, for example, about 2 μm. It is what has. Here, the film thickness of the carbon thin film layer 22 to be formed is set smaller than the radius of the opening in the first porous resin material. For this reason, even after the carbon thin film layer 22 is formed, the opening on the facing surface is prevented from being completely blocked.

  The carbon rod 23 has a slightly larger outer dimension than the through hole 21 c formed in the main body 21 and a slightly larger length than the thickness dimension of the main body 21. The carbon rod 23 is press-fitted into the through hole 21 c of the main body 21. The carbon rod 23 is integrally joined to the carbon thin film 22. Hereinafter, this bonding will be described.

  In producing the gas diffusion layer 20, first, the carbon rod 23 is press-fitted into each of the through holes 21 c of the main body 21. Next, carbon is vapor-deposited on the opposing surface by sputtering to the main body 21 into which the carbon rod 23 is press-fitted to form the carbon thin film layer 22. Here, according to the sputtering method, by using the carbon base material as a target, carbon atoms are blown off from the surface of the carbon base material, and the carbon atoms reaching the opposing surface of the main body 21 form the carbon thin film layer 22. can do. At this time, since the incoming carbon atoms are the same as those of the carbon rod 23, the carbon atoms colliding with the carbon rod 23 form a carbon thin film layer 22 while being integrated. That is, since the carbon thin film layer 22 and the carbon rod 23 are made of the same material (carbon), they can be joined together without forming an interface between the carbon thin film layer 22 and the carbon rod 23.

  In the present embodiment, the carbon thin film layer 22 is formed by vapor deposition of carbon using a sputtering method, but other methods (for example, an ion plating method or the like) are used to form the main body 21. It is also possible to form the carbon thin film layer 22 on the opposite surface by vapor deposition. As described above, even when the carbon thin film layer 22 is formed by vapor deposition using another method, the carbon thin film layer 22 and the carbon rod 23 can be integrally joined without forming an interface. it can.

  In this embodiment, the carbon thin film layer 22 is formed by vapor deposition of carbon. For example, the carbon thin film layer 22 is formed on the opposing surface of the main body 21 by applying carbon. It is also possible to carry out. In this case, an interface may be formed between the applied carbon and the carbon thin film layer 22 and the carbon rod 23 can be integrally joined since they are made of the same material.

  The current collecting plate 30 has a function of preventing a mixed flow of fuel gas and oxidant gas introduced from the outside of the fuel cell and a function of collecting electricity generated by an electrode reaction in the MEA 10. Further, depending on the configuration, it also has a function of preventing the cooling water for cooling the fuel cell from entering the single cell T. For this reason, the current collecting plate 30 is formed of, for example, a stainless steel thin plate, and sandwiches the MEA 10 with the gas diffusion layer 20 interposed therebetween. By sandwiching the MEA 10 and the gas diffusion layer 20 in this manner, the current collector plate 30 comes into contact with the carbon rods 23 of the gas diffusion layer 20 as shown in FIG. As a result, the current collector plate 30 is electrically connected to the MEA 10 via the carbon thin film layer 22 and the carbon rod 23 excellent in conductivity of the gas diffusion layer 20, so that the generated electricity is efficiently collected. Can be output externally.

  The current collecting plate 30 can be formed of a thin steel plate subjected to anticorrosion treatment such as gold plating or nickel plating, for example, instead of the above-described stainless steel thin plate. In addition, the current collecting plate 30 can be formed of a non-metallic thin plate such as carbon having excellent conductivity instead of the metal.

  A plurality of single cells T configured as described above are stacked according to the required output of the fuel cell to form a stack of fuel cells. When the fuel gas and the oxidant gas are introduced into the fuel cell stack, power is generated by causing an electrode reaction on the anode electrode side and the cathode electrode side of the MEA 10 of each single cell T. Hereinafter, this electrode reaction will be described.

As described above, in the polymer electrolyte fuel cell in which the electrolyte membrane 11 of the MEA 10 is formed of an ion exchange membrane that selectively transmits hydrogen ions (H ⁺ ), a fuel gas (hydrogen gas) and an oxidant gas ( When air is supplied, reactions shown by the following chemical reaction formulas 1 and 2 occur in the catalyst layer 12 on the anode electrode side and the catalyst layer 13 on the cathode electrode side, respectively.
Anode electrode side: H ₂ → 2H ⁺ + 2e ⁻ … chemical reaction formula 1
Cathode electrode side: 2H ⁺ + 2e ⁻ + (1/2) O ₂ → H ₂ O… chemical reaction formula 2

Specifically, the electrode reaction in the catalyst layer 12 on the anode electrode side will be described. Hydrogen gas introduced from the outside of the fuel cell is prevented from being mixed with air by the current collecting plate 30, and the gas diffusion layer 20. The inside of the main body 21 is conducted. At this time, since the main body 21 is formed of a porous resin material, the fuel gas is appropriately diffused by being conducted through the main body 21 and supplied to the catalyst layer 12 of the MEA 10 from the facing surface. Here, the opposing surface of the main body 21 is formed so that the film thickness of the carbon thin film layer 22 is smaller than the radius of the opening in the opposing surface, in other words, the opening is not blocked. Is supplied over the entire surface of the catalyst layer 12. Thereby, the chemical reaction formula 1 is generated, and the hydrogen gas is ionized into hydrogen ions (H ⁺ ) and electrons. The ionized hydrogen ions (H ⁺ ) pass through the electrolyte membrane 11 of the MEA 10 and move to the cathode electrode side, and the ionized electrons are supplied to the cathode electrode side catalyst layer 13 via an external circuit (not shown). .

  Incidentally, the catalyst layer 12 is in contact with the entire surface of the carbon thin film layer 22 of the gas diffusion layer 20. For this reason, the ionized electrons can move very easily from the catalyst layer 12 to the carbon thin film layer 22 having excellent conductivity. The carbon thin film layer 22 and the carbon rod 23 are both made of carbon, and are integrally joined. Thereby, the electrons moved to the carbon thin film layer 22 can move to the current collecting plate 30 by moving the carbon rod 23 very easily. And since the carbon rod 23 is provided with two or more, the contact state (contact area) between the carbon rod 23 and the current collecting plate 30 is ensured favorably. For this reason, the contact resistance between the carbon rod 23 and the current collector plate 30 is reduced, and electrons easily move from the carbon rod 23 toward the current collector plate 30, and the catalyst layer on the cathode electrode side via an external circuit. Electrons sufficient for the electrode reaction at 13 can be transferred.

Next, an electrode reaction in the catalyst layer 13 on the cathode electrode side will be described. The air introduced from the outside of the fuel cell is conducted through the main body 21 of the gas diffusion layer 20 in a state in which mixed current with hydrogen gas is prevented by the current collector plate 30. At this time, since the main body 21 is formed of a porous resin material, the air is appropriately diffused by conducting through the main body 21 in the same manner as the fuel gas supplied to the anode electrode side, and the MEA 10 from the opposite surface. Is supplied over the entire surface of the catalyst layer 13. As a result, the chemical reaction formula 2 is generated and supplied from the oxygen in the supplied air, the hydrogen ions (H ⁺ ) permeated through the electrolyte membrane 11 from the anode electrode side, and the catalyst layer 12 on the anode electrode side. Generate water from electrons.

  Here, also on the cathode electrode side, the gas diffusion layer 20 has the same configuration as that on the anode electrode side. For this reason, the electrons supplied through the external circuit can easily move from the current collector 30 toward the carbon rod 23. Further, since the carbon rod 23 and the carbon thin film layer 22 are integrally joined, electrons can move from the carbon rod 23 to the carbon thin film layer 22 very easily. Further, the carbon thin film layer 22 is in contact with the entire surface of the catalyst layer 13. For this reason, the electrons supplied from the catalyst layer 12 on the anode electrode side can very easily move from the carbon thin film layer 22 to the catalyst layer 13. Thus, the electrode reaction represented by the chemical reaction formulas 1 and 2 is appropriately generated as long as hydrogen gas and air are supplied. As a result, the fuel cell can generate electricity.

By the way, when the electrode reaction represented by the chemical reaction formula 1 occurs, hydrogen ions (H ⁺ ) ionized by the catalyst layer 12 on the anode electrode side move together with water in the electrolyte membrane 11 toward the cathode electrode side. . In other words, hydrogen ions (H ⁺ ) move from the anode electrode side to the cathode electrode side by hydrating with water retained in the electrolyte membrane 11. For this reason, the moisture content of the electrolyte membrane 11 on the anode electrode side decreases as the electrode reaction proceeds.

As described above, when the moisture content of the electrolyte membrane 11 is reduced (so-called dry-up state), there is not enough water for hydrogen ions (H ⁺ ) to move. As a result, the electrical resistance when hydrogen ions (H ⁺ ) permeate the electrolyte membrane 11 increases, and the power generation efficiency of the fuel cell may decrease. Therefore, generally, when supplying hydrogen gas to the anode electrode, in order to eliminate the dry-up state of the electrolyte membrane 11, for example, hydrogen gas to which humidified water (water vapor or mist) is applied by a separately provided humidifier is used. It comes to be supplied.

  On the other hand, in the catalyst layer 13 on the cathode electrode side, when the electrode reaction represented by the chemical reaction formula 2 occurs, water is generated. Therefore, the generated water (hereinafter referred to as generated water) needs to be drained. . That is, if the generated water accumulates in the vicinity of the catalyst layer 13, it is difficult for air to reach the catalyst layer 13, and the power generation efficiency of the fuel cell may be reduced.

  With regard to these matters, the main body 21 of the gas diffusion layer 20 has the first layer 21a having a large opening radius on the side facing the MEA 10 as described above, and the opening radius on the current collecting plate 30 side. A small second layer 21b is arranged. Thereby, when the hydrogen gas provided with humidified water is supplied to the anode electrode side, since the radius of the opening of the opposing surface, that is, the first layer 21a is large, the humidified water can be supplied together with the hydrogen gas, The above-described dry-up state can be appropriately suppressed. On the other hand, when generated water is generated on the cathode electrode side, first, the generated water is absorbed by a large number of holes formed in the first layer 21a, and then formed in the second layer 21b having a small opening radius. The generated water is absorbed by a large number of holes.

  That is, in the situation where generated water exists on the surface of the catalyst layer 13, first, a capillary phenomenon due to the first layer 21 a occurs, and the generated water moves from the surface of the catalyst layer 13 into the first layer 21 a. When the generated water moves into the first layer 21a, the generated water in the first layer 21a moves toward the second layer 21b by the second layer 21b in which the opening radius is small and the capillary phenomenon is generated more strongly. become. Thereby, since the generated water existing on the surface of the catalyst layer 13 and in the first layer 21 a is absorbed by the second layer 21 b, air introduced from the outside can be satisfactorily supplied to the catalyst layer 13. it can. The generated water absorbed by the second layer 21b is drained from the main body 21 to the outside by the pressure of the introduced air, as shown in FIG. As described above, since the water retention on the anode electrode side and the drainage on the cathode electrode side can be appropriately performed, it is possible to effectively suppress a decrease in power generation efficiency in the fuel cell.

  As can be understood from the above description, according to the present embodiment, the gas diffusion layer 20 can be formed using an inexpensive and light non-conductive porous resin material. Thereby, there is no elution of metal ions, and the durability of the fuel cell can be sufficiently ensured. Moreover, in order to ensure the conductivity of the gas diffusion layer 20 formed from a non-conductive porous resin material, carbon having excellent conductivity was used on the facing surface of the main body 21 facing the MEA 10. The carbon thin film layer 22 can be formed. By forming the carbon thin film layer 22 having conductivity on the entire surface of the opposing surface, it is possible to satisfactorily ensure the contact state (contact area) between the catalyst layers 12 and 13 of the MEA 10 and the carbon thin film layer 22. it can. Thus, the generated electricity (more specifically, electrons generated by the electrode reaction) is transferred from the catalyst layer 12 on the anode electrode side to the carbon thin film layer 22 or from the carbon thin film layer 22 to the catalyst layer 13 on the cathode electrode side. Loss can be reduced and transmitted.

  In forming the carbon thin film layer 22, the film thickness is formed to be smaller than the radius of the opening in the facing surface of the main body 21. As a result, the formed carbon thin film layer 22 can be prevented from closing the opening on the opposing surface, and the fuel gas and the oxidant gas that are conducted through the main body 21 are supplied to the MEA 10 (more specifically, the catalyst layers 12 and 13). In contrast, sufficient supply is possible.

  In addition, since the carbon rod 23 formed of carbon, which is the same material, can be integrally joined to the carbon thin film layer 22 to be formed, the contact resistance between the carbon thin film layer 22 and the carbon rod 23 Can be substantially “0”. Therefore, the generated electricity (more specifically, electrons generated by the electrode reaction) can be transmitted without loss from the carbon thin film layer 22 to the carbon rod 23 or from the carbon rod 23 to the carbon thin film layer 22. And since the carbon rod 23 can penetrate the main body 21 and can electrically connect the carbon thin film layer 22 and the current collector plate 30, it can efficiently output the generated electricity via the current collector plate 30. it can.

  In forming the carbon thin film layer 22, the carbon thin film layer 22 can be formed by depositing the carbon rod 23 into the main body 21 and depositing carbon on the opposing surface by a sputtering method. Thereby, the carbon thin film layer 22 and the carbon rod 23 can be reliably integrated and bonded, and the smooth carbon thin film layer 22 having a uniform layer thickness can be formed. Therefore, the contact state (contact area) between the catalyst layers 12 and 13 of the MEA 10 and the carbon thin film layer 22 can be secured better, and the conductivity of the gas diffusion layer 20 can be secured better. In addition, since a uniform layer thickness can be ensured, the carbon thin film layer 22 can be more reliably prevented from closing the opening on the opposing surface of the main body 21.

  A plurality of carbon rods 23 can be provided. Thereby, since the contact part of the carbon rod 23 and the current collector plate 30, in other words, the contact area can be increased, the contact resistance between the carbon rod 23 and the current collector plate 30 can be further reduced. . Therefore, the generated electricity can be output more efficiently via the current collector plate 30.

  Moreover, the displacement of the carbon rod 23 relative to the main body 21 can be regulated by press-fitting the carbon rod 23 into the through hole 21 c formed in the main body 21. Thereby, even when the fuel cell stack is formed, the contact state of the carbon rod 23 with respect to the carbon thin film layer 22 and the current collector plate 30 (particularly, the contact state between the carbon rod 23 and the current collector plate 30). Can be maintained well. Therefore, the generated electricity can be output efficiently over a long period of time.

  Moreover, since the main body 21 can be formed from the first layer 21a and the second layer 21b, the radius of the opening in the main body 21 can be made very different easily and inexpensively on the MEA 10 side and the current collector plate 30 side. Can do. Therefore, the main body 21 can absorb the generated water generated on the cathode electrode side by the electrode reaction in the MEA 10 to a position away from the catalyst layer 13. Further, since the radius of the opening on the opposing surface of the main body 21 is increased, it is possible to effectively prevent the opening from being blocked even if the carbon thin film layer 22 is formed. Therefore, the main body 21 can satisfactorily supply the fuel gas (hydrogen gas) or the oxidant gas (air) to the catalyst layers 12 and 13, and as a result, suppresses a decrease in the power generation efficiency of the fuel cell. Can do.

  In carrying out the present invention, the present invention is not limited to the above embodiment, and various modifications can be made.

  For example, in the above embodiment, the carbon thin film layer 22 that is in contact with the entire catalyst layers 12 and 13 of the MEA 10 forming the single cell T is formed, and the carbon thin film layer 22 and the current collector plate 30 are connected to the carbon rod. 23, and electrically connected via 23. On the other hand, since the main body 21 is formed from a non-conductive porous resin material, as shown in FIG. 3, one catalyst layer 12 and 13 is divided using an insulator, and this division is performed. The carbon thin film layers 221, 222 are formed by dividing one carbon thin film layer 22 using an insulator so as to be in contact with the catalyst layers 121, 122, 131, 132, and the carbon thin film layers 221, 222, It is also possible to divide one current collecting plate 30 using an insulator so as to be electrically connected via the carbon rod 23 and to provide the current collecting plates 301 and 302.

  In this way, the single cell T is electrically divided by forming the catalyst layers 121, 122, 131, 132, the carbon thin film layers 221, 222, and the current collecting plates 301, 302 by dividing them with the insulator. Can do. Thereby, for example, by appropriately changing the connection mode by an external circuit, it is possible to connect electrically in series or in parallel in the single cell T, or to change the voltage in the single cell T. Become. Therefore, in addition to the effect in the above-described embodiment, for example, the effect that it is possible to supply electricity required by one fuel cell can be expected even when the installation space of the fuel cell is limited.

  In the above embodiment, the catalyst layers 12 and 13 are integrally formed on the electrolyte membrane 11. However, after the carbon thin film layer 22 of the gas diffusion layer 20 is formed, the catalyst layers 12 and 13 may be integrally formed on the carbon thin film layer 22 so as to sandwich the electrolyte membrane 11. . In this case, the catalyst layers 12 and 13 may be formed in advance in a sheet shape, for example, and the sheet-like catalyst layers 12 and 13 may be attached to the carbon thin film layer 22. Thereby, the contact resistance between the catalyst layers 12 and 13 and the carbon thin film layer 22 can be further reduced.

Moreover, in the said embodiment, it implemented so that the electrolyte membrane 11 might be formed from the ion exchange membrane which permeate | transmits hydrogen ion (H ⁺ ) selectively. In addition, a non-metallic carbon thin film layer 22 was formed as a thin film layer of the gas diffusion layer 20. As a result, elution of metal ions into the electrolyte membrane 11 was prevented, and the durability of the fuel cell was sufficiently ensured.

By the way, when the electrolyte membrane is formed from an ion exchange membrane (for example, Neoceptor (registered trademark) manufactured by Tokuyama Corporation) that selectively transmits anions (more specifically, hydroxide ions (OH ⁻ )). Can also be implemented so that the thin film layer and the conductive member on the side of the gas diffusion layer facing the anode electrode are formed using a hydrogen storage alloy. In this case, since the hydroxide ions (OH ⁻ ) move in the electrolyte membrane, the surrounding environment of the MEA becomes alkaline. Thereby, since corrosion of a metal is suppressed, elution of metal ions to the electrolyte membrane can be prevented, and the durability of the fuel cell can be sufficiently ensured.

  Moreover, in the said embodiment, it implemented so that the main body 21 might be formed from the 1st layer 21a and the 2nd layer 21b. That is, in the said embodiment, it implemented so that the main body 21 might be formed using the 1st porous resin material which forms the 1st layer 21a, and the 2nd porous material which forms the 2nd layer 21b. On the other hand, it cannot be overemphasized that the main body 21 can be formed and formed from a single porous resin material. In this case, although the radius of the opening is the same and the water absorption characteristic of the main body 21 with respect to the water generated on the cathode electrode side described above may be slightly deteriorated, the same effect as in the above embodiment can be expected. Even when the main body 21 is formed from a single porous resin material in this way, for example, it is preferable to increase the radius of the opening from the current collector 30 side toward the MEA 10 side.

  Moreover, in the said embodiment, the main body 21 was formed with two layers, the 1st layer 21a and the 2nd layer 21b, and implemented. However, as long as the first layer 21a and the second layer 21b are included, the number of layers forming the main body 21 is not limited to two.

  Furthermore, with respect to the gas diffusion layer 20 in the above-described embodiment, for example, it is possible to form a flow path for circulating a gas introduced from the outside. Specifically, a flow path may be formed in the first layer 21 a in the main body 21 of the gas diffusion layer 20. In this case, as a flow path to be formed, for example, a groove-shaped flow path extending from the gas introduction position toward the discharge position may be formed.

It is sectional drawing which showed the schematic structure of the single cell which concerns on embodiment of this invention. It is an enlarged view for demonstrating the structure of the gas diffusion layer of FIG. It is sectional drawing which showed the schematic structure of the single cell which concerns on the modification of this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 ... MEA, 11 ... Electrolyte membrane, 12 ... Catalyst layer (anode electrode side), 13 ... Catalyst layer (cathode electrode side), 20 ... Gas diffusion layer, 21 ... Main body, 21a ... First layer, 21b ... Second layer , 22 ... carbon thin film layer, 23 ... carbon rod, 30 ... current collector plate

Claims (9)

It is disposed between an electrode catalyst layer constituting an electrode structure of a fuel cell and a current collector that collects electricity generated by the electrode structure, and diffuses a predetermined gas to the electrode catalyst layer. In the fuel cell gas diffusion layer to supply
A flat body formed of a non-conductive porous resin material, which diffuses the predetermined gas and conducts;
A conductive thin film layer formed on an opposing surface of the main body facing the electrode catalyst layer and having a thickness smaller than the radius of the opening on the opposing surface;
A conductive member formed of the same material as the thin film layer, electrically connecting the thin film layer and the current collector through the body and contacting the electrode catalyst layer;
A gas diffusion layer for a fuel cell, wherein the thin film layer and the conductive member are integrally joined. In the gas diffusion layer for a fuel cell according to claim 1,
The thin film layer is
A gas diffusion layer for a fuel cell, wherein the conductive member is formed on the facing surface of the main body in a state of passing through the main body. In the gas diffusion layer for a fuel cell according to claim 2,
The thin film layer is
A gas diffusion layer for a fuel cell, which is formed by vapor deposition on the facing surface of the main body. In the gas diffusion layer for a fuel cell according to claim 1,
A gas diffusion layer for a fuel cell, wherein a plurality of the conductive members are provided for the main body. In the gas diffusion layer for a fuel cell according to claim 4,
The conductive member is formed in a rod shape,
A gas diffusion layer for a fuel cell, wherein a plurality of gas diffusion layers are press-fitted into a plurality of through holes formed in the main body. In the gas diffusion layer for a fuel cell according to claim 1,
The gas diffusion layer for a fuel cell, wherein the thin film layer and the conductive member are made of carbon. In the gas diffusion layer for a fuel cell according to claim 1,
The electrocatalyst layer is electrically divided within the layer;
A gas diffusion layer for a fuel cell, wherein the thin film layer and the current collector are electrically divided corresponding to the divided electrode catalyst layers. In the gas diffusion layer for a fuel cell according to claim 1,
The body is
A gas diffusion layer for a fuel cell, wherein the gas diffusion layer is formed of a porous resin material having an opening radius that increases from the current collector toward the electrode catalyst layer. The gas diffusion layer for a fuel cell according to claim 8,
The body is
A first layer disposed on the electrode catalyst layer side and formed from a first porous resin material having a large opening radius;
And a second layer formed of a second porous resin material disposed on the current collector side and having an opening radius smaller than that of the first porous material. Gas diffusion layer.

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